Plasma is typically generated using a capacitively-coupled plasma (CCP) source or an inductively-coupled plasma (ICP) source. A basic CCP source contains two metal electrodes separated by a small distance in a gaseous environment similar to a parallel plate capacitor. One of the two metal electrodes are driven by a radio frequency (RF) power supply at a fixed frequency while the other electrode is connected to an RF ground, generating an RF electric field between the two electrodes. The generated electric field ionizes the gas atoms, releasing electrons. The electrons in the gas are accelerated by the RF electric field and ionizes the gas directly or indirectly by collisions, producing plasma.
A basic ICP source typically contains a conductor in a spiral or a coil shape. When an RF electric current is flowed through the conductor, RF magnetic field is formed around the conductor. The RF magnetic field accompanies an RF electric field, which ionizes the gas atoms and produces plasma.
Plasmas of various process gasses are widely used in fabrication of integrated circuits. Plasmas can be used, for example, in thin film deposition, etching, and surface treatment.
Atomic layer deposition (ALD) is a thin film deposition technique based on the sequential use of a gas phase chemical process. Some ALD processes use plasmas to provide necessary activation energy for chemical reactions. Plasma-enhanced ALD processes can be performed at a lower temperature than non-plasma-enhanced (e.g., ‘thermal’) ALD processes.